The present invention is directed to the field of precision fastening. More particularly, the present invention is directed to a precision locating and fastening system particularly useful in securing work pieces to a work holder for machining operations.
Currently, devices for locating and anchoring articles include dowel pins, a variety of fasteners including shoulder bolts, key ways including T-keys and T-bolts, for example. Dowel pins and other fasteners are adequate for some applications but are not without their limitations. Firstly, when quick connect/disconnect is desired, dowel pins and threaded fasteners typically are found wanting. Dowel pins, for example, require application of axial force and removing the dowels can be time consuming. Typically, dowel pins are used for locating an article and other forms of fasteners are used to secure the item. This use of two different systems mitigates against a quick connect/disconnect.
Shoulder bolts can be used for both locating and fastening. A shoulder bolt is asked to do both the aligning of the attached articles and the fastening/securing of those items. Accordingly, when there is misalignment between the attached article and the base, the threads of the shoulder bolt can bind in the hole. If thread advancement is forced, galling of the holes and stripping of threads can occur. Alternatively, or in addition, damage to the shoulder of the bolt can occur as it is pushed and rotated into the mis-aligned opening.
Keys and key ways are also used for locating and attaching articles to base members.
However, such means of locating/attaching can be costly to machine onto both items and certainly, does not provide a form of quick connect/disconnect.
A popular locating and fastening system is the Jergen's Ball Lock mounting system. The ball lock is inserted into the mounting hole until its shoulder engages against the accessory, etc., and then a screw with an angled surface is actuated driving three balls against a complimentary angle in the mating accessory. One of the main problems with this system is that resulting binding can make it difficult to insert and remove this system making its use cumbersome and time consuming.
The locator/fastener system of the present invention overcomes these problems and difficulties. The locating and fastening functions are performed by separate elements of the device with the fastener captured within the locator in a manner enabling it to float, so that the fastener has the freedom to engage the threads in the receiver without binding or galling.
A first aspect of the invention comprises a system for precisely positioning and fastening an article to a base, the system including a locator having a retention head on a trailing end portion, a cylindrical body portion with a leading end portion and a precision-machined external surface adapted to fit within an opening of the article to be precisely located, the locator having an internal axial throughbore. Fastening means is received within the axial throughbore such that an attachment portion extends axially beyond the leading end portion of the locator. Retention means secures the fastening means within the internal axial throughbore; whereby a portion of the cylindrical body portion of the locator extends through the article to be precisely located and is received in a precision-machined internal opening of the base and the attachment portion is securely engaged in the base to retain the article in position relative thereto.
The retention means secures the fastening means within the internal axial throughbore in a manner permitting the fastening means to float relative to the locator. The fastening means is preferably a cap screw and the internal axial throughbore has multiple diameters, a first larger diameter to receive the head of the cap screw and the second to receive the threaded body portion thereof. One preferred drive for the cap screw is an internal hex recess. One form of the retention means comprises a spring clip which engages in a slot formed in the retention head of said locator. It will be understood that other retention means could be used without affecting the operation of the device and the retention means could engage other portions of the fastening means, the projecting portion of the fastener, for example.
The retention head of the locator is preferably formed with an undercut whereby tightening the locator onto the article provides a spring pressure generally equivalent to that provided by a lock washer. The system preferably includes a receiver having external threads for engaging in a tapped recess in the base and has the precision-machined internal opening as a first portion of a stepped axial throughbore, the first portion receiving the precision machined external surface of the locator, a second portion of the stepped axial throughbore receiving the attachment portion of the fastening means. The receiver preferably includes a radially extending head portion surrounding a major axial length of the first portion of the stepped recess, the radially extending head portion cooperating with the retention head of the locator to precisely clamp the article relative to the base. Preferably, the receiver is made of metal which has been treated to harden it.
In a second aspect of the invention, the system for precisely positioning and fastening an article to a base, the article having at least one first throughbore with a first center-line and the base having at least one second throughbore with a second center-line, where the system includes a locator having a cylindrical body portion with a leading end portion and a precision-machined external surface adapted to fit within an opening of the article to be precisely located, the locator having an internal axial throughbore; fastening means; a hardened receiver having an externally threaded cylindrical body, a radially extending head portion and having a precision-machined internal opening as a first portion of a stepped axial throughbore, the precision-machined internal opening receiving at least a portion of the precision-machined external surface of the locator, and a second portion of the stepped axial throughbore receiving and securing a portion of the fastening means. The outer peripheral edge of the leading end portion of the locator has a first angular surface formed thereon and a second complementarily angular surface is formed within a leading internal surface of the receiver, a radial extent of the first and second angular surfaces determining an amount of misalignment between the first center-lines and the second-center lines which can be corrected.
In a third aspect of the invention, the system for precisely positioning and fastening at least one article to a base plate includes a sub-base plate removably attached to the base plate, said sub-base plate having i) at least one throughbore with a first center-line, and, ii) means by which the at least one article is attached thereto; b) at least one docking stud attached to the sub-base by which the sub-base is proximately positioned relative to and secured to the base plate; a v-shaped docking stud notch for receiving the at least one docking stud and supporting the sub-base; d) fastening means for engaging attaching the sub-base to the base. Preferably, the fastening means includes at least one locator/fastening means with a precision-machined external surface for engaging in the throughbore in the sub-base plate, the throughbore being a precision-machined throughbore.
Preferably, each locator/fastener means includes a locator having a retention head on a trailing end portion, a cylindrical body portion with a leading end portion and a precision-machined external surface adapted to fit within the precision-machined throughbore in the sub-base, the locator having an internal axial throughbore. Fastening means is received within the axial throughbore such that an attachment portion extends axially beyond the leading end portion of the locator and retention means secures the fastening means within the internal axial throughbore. It is desired that a first angular surface be formed on an outer peripheral edge of the leading end portion of the locator and a second complementarily formed angular surface be formed within a leading internal surface of the receiver, a radial extent of said first and second angular surfaces determining an amount of misalignment between the first center-lines and the second-center lines which can be corrected. The docking stud notch is preferably made of hardened material separate from the base plate and is secured thereto by threaded fasteners.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.